The present invention relates to a device for dispensing of hydrogen, in particular for supplying gaseous hydrogen for a fuel cell.
Metal hydride storage devices in which the actual storage material is usually magnesium or nickel are known for temporary storage of hydrogen. To unload hydrogen stored in such a metal hydride storage device, it is usually heated to a temperature of approximately 300xc2x0 C. In addition, because of the required heat management in loading and unloading with hydrogen due to the heat of adsorption and desorption, the storage material is often embedded in an uninterrupted aluminum foam structure.
In addition to metal hydride storage devices for hydrogen, there are also known cryostorage devices in which cooled, liquefied hydrogen is stored at temperatures of around 20 K; there are also known carbon nanostorage devices, storage devices based on glass microbeads and traditional gas pressure tanks for hydrogen.
An object of the present invention is to provide a device for dispensing hydrogen which would have an improved energy efficiency in comparison with that known in the related art and would also consume less energy in heating the device to the required operating temperature in comparison with the related art.
The device according to the present invention for dispensing hydrogen has the advantage over the related art that due to the modular design, the entire device need not be heated constantly or completely each time in heating to the operating temperature of 300xc2x0 C., for example, for dispensing hydrogen.
Thus, in heating conventional metal hydride storage devices, approximately 4% of the energy content of the full hydrogen storage device is consumed in each heating operation, so that these systems have a very poor energy efficiency on the whole. Furthermore, due to the large mass of the known storage devices to be heated, in particular when they are used to supply gaseous hydrogen for a fuel cell in a motor vehicle, a longer waiting time is necessary with a cold start, leading to an unacceptable impairment in operation of a motor vehicle.
The device according to the present invention, however, drastically reduces the energy consumption in heating to the operating temperature and shortens the required waiting time with a cold start.
In addition, the device according to the present invention for delivering hydrogen also offers considerable advantages in comparison with conventional cryostorage devices with regard to energy efficiency, because cryostorage devices need approximately 40% of the energy of the stored hydrogen for constant cooling of the hydrogen to approximately 20 K, and in addition approximately 1% to 2% of the stored hydrogen evaporates per day with such a storage device. Therefore, because of the wide ignition range of hydrogen, it is impossible to park vehicles equipped with a cryostorage device in a garage or a multistory parking garage.
In contrast to carbon nanostorage devices, the device according to the present invention has the advantage that the storage capacity is greatly increased, while also having the advantage of a significantly more rapid release of gas in comparison with storage of hydrogen with the help of glass microbeads.
In particular, due to the fact that the gas reservoir of the device according to the present invention is subdivided into multiple modules, each being heatable independently of the others, this yields the result that only a small partial area of the reservoir need be heated to provide the hydrogen instantaneously required in operation of this device. Furthermore, due to the smaller mass of the hydrogen to be heated, preferably in just one module at first, with the device according to the present invention, the required hydrogen is available practically immediately even with a cold start of a motor vehicle.
It is especially advantageous if the individual modules are designed like previously known metal hydride storage devices and preferably contain magnesium and nickel as the metal which stores hydrogen in the form of a metal hydride. In addition, it is advantageous if these individual modules, in accordance with the known metal hydride storage devices, have a foam structure, in particular an aluminum foam structure in which the metal storing the hydrogen temporarily is embedded.